The strong growth in number of Internet users has been one of the most remarkable phenomena in communications in recent years. The rapid growth has also highlighted defects on the Internet. One of these is the poor data security of the network. The IP protocol version (IPv4) now in general use does not provide any such means, with which it would be possible to make sure that information arrived from the opposite end did not change during the transfer or that the information did in fact arrive from that source, who claims to have sent the information in question. In addition, it is easy to use various tools in the network for listening in to the traffic. For these reasons, those systems are very vulnerable which transmit non-encrypted critical information, e.g. passwords.
The new IP version (IPv6) has internal characteristics that allow safe communication between Internet users. Because the transition to the new protocol will be slow, the data security features should be such that they are compatible with the present IP version (IPv4), and so that they can be added to this.
Various such systems have been developed to improve the data security properties of the Internet where users can send the information encrypted to the other party. One such system is the Kerberos, which is a service with which network users and services can authenticate one another and with which users and services can bring about encrypted connections between each other. The Kerberos system is utilised in one embodiment of the present invention which will be described more closely hereinafter.
Another current trend is the strongly increasing use of various mobile terminals. Along with this trend it is even more important that the terminals will have access to the data network also when being located outside their own home network. Such an access can essentially improve the usability of e.g. a portable computer, when the user is not in his/her usual working environment Points of access may be located e.g. at airports, in railway stations, in shopping malls or on any other public premises, and the access may be wired or wireless.
Systems of the described kind, which can be used for sending encrypted information between parties, are mainly intended for fixed terminals and they require that the users are registered in advance as users of the service. It is a problem nowadays that for IP networks supporting mobility of the terminals there is no such existing and functioning authentication or key management system that would guarantee good geographical coverage and at the same time allow the user easily to have an authenticated and safe connection available to himself/herself in an area which is geographically as large as possible.